1. Field of the Invention
The invention relates to standards used in assaying for triglyceride levels.
2. Description of the Prior Art
The prior art is believed best set forth in U.S. Pat. No. 3,853,465, which is hereby incorporated by reference. Generally this patent sets forth the facts of difficulties in photometric analysis which result from turbidity in serum and plasma samples. This is due primarily to triglycerides present in the serum. The solution to this turbidity problem which U.S. Pat. No. 3,853,465 sets forth is to add a surfactant to the serum or plasma to reduce the turbidity. This patent discloses a surfactant of polyoxyethylated lauric acid having from 9 to 20 ethoxy groups. Compounds of this general class which have from 10 to about 20 ethoxy groups are disclosed in U.S. Pat. No. 3,260,648 for use as an emulsifier for cholesterol in serum. This latter patent sets forth the use of a lower alkylphenoxypolyethoxyethanol having from about 10 to about 20 ethoxy groups. While the use of such surfactants does result in an improvement in turbidity in serum, the products produced tend to be metastable and separate after a period of time. Additionally, large amounts of surfactant are generally required and such large amounts of surfactant interfere with biological assays of serum ingredients. Moreover, even with the surfactants of this type, reconstitution of lyophilized serum having elevated triglyceride levels produces measurable turbidity notwithstanding the use of the surfactants.
In addition to the above-mentioned patents, a triglyceride standard is disclosed in an article by Chong-Kit and McLaughlin published in Clinical Chemistry, Volume 20, No. 11 (1974). This standard uses triolein emulsified with isooctylphenoxypolyethoxyethanol having an average of 9 to 10 ethylene oxide groups. This standard is prepared by heating to elevated temperatures and mixing triolein with the surfactant. This mixture is also metastable and tends to become cloudy with time. More importantly, it cannot be frozen or lyophilized and then reconstituted or thawed without producing a cloudy solution. Even more importantly, the temperatures set forth for manufacturing the standard are too high to permit the procedure to be used with serum without risking destruction of enzymes desired in the serum.